INFERENTIAL STATISTICS Extra Credit #2

Mark W. Tengler, M.S.
PSYC 4730
INFERENTIAL STATISTICS
Extra Credit #2
Directions:
Answer the questions with the data that is given and only using your formula
worksheets and the tables in the back of the book (t Distribution and F
Distribution tables). Please show the complete design and your work. Please
set up tables to do your calculations similarly to how we did it in class, and then
plug the numbers into the correct formulas. Please work individually. This
exercise is worth 10 points extra credit and is due on the final exam day.
Ch. 9: Numerous studies have shown that IQ scores have been increasing, generation by
generation, for years (Flynn, 1984, 1999). The increase is called the Flynn Effect, and the
data indicate that the increase appears to be about 7 points per decade. To
demonstrate this phenomenon, a researcher obtains an IQ test that was written in
1980. At the time the test was prepared, it was standardized to produce a population
mean of µ = 100. The researcher administers the test to a random sample of n = 16 of
today’s high school students and obtains a sample mean IQ of M = 121 with SS = 6000.
Is this result sufficient to conclude that today’s sample scored significantly higher than
would be expected from a population with µ = 100? Use α = .01.
Ch. 10: A biopsychologist studies the role of the brain chemical serotonin in aggression. One
sample of rats serves as a control group and receives a placebo. A second sample of rats
receives a drug that lowers brain levels of serotonin. Then the researcher tests the
animals by recording the number of aggressive responses each of the rats display. For
the data below, is there a significant effect of the drug on aggression? What, if any, role
does serotonin have in aggression? Use an alpha level of α = .05. (note: is this a one-tail or
two-tail test?)
Lowers Serotonin
5
8
15
16
6
9
(see next page for more)
1
Control
3
6
5
6
8
4
7
Mark W. Tengler, M.S.
PSYC 4730
Ch. 13: A developmental psychologist is examining problem-solving ability for grade school
children. Random samples of 5-year old, 6-year old, and 7-year old children are
obtained with n = 3 in each sample. Each child is given a standardized problem-solving
task, and the psychologist records the number of errors. The data are as follows:
5-year olds
5
4
6
a.
6-year olds
6
4
2
7-year olds
0
1
2
Does the data indicate whether there are any significant differences among the
three age groups? Use α = .05. Show the complete design, all your work, and
report your results professionally.
Ch. 14: Complete the matrix for the following scenario:
A researcher conducted a two-factor research study using two levels of diet and four
levels of exercise with a sample size of n = 6 for each of the unique treatment conditions
(i.e. for each group). The table summarizes the results of the analysis, but it is not
complete. Fill in the missing values. (Hint: Start with the df values first, which you can
calculate from your formula sheet.) Show your work and all calculations.
s2 or MS
F ratio
______
______
F = ______
______
______
48
F = ______
120
______
______
F = ______
______
______
______
600
______
Source
SS
df
Between groups
280
______
Main effect of diet
______
Main effect of
exercise
Diet x Exercise
interaction
Within groups
Total
2